- Cnicus benedictus L.
- Bitter thistle, Carbenia benedicta, cardin, Cardo Santo, Carduus benedictus, Chardon Benit, Cnici benedicti herba, cnicus, holy thistle, Kardo-benedictenkraut, St. Benedict thistle, salonitenolide, spotted thistle.
- Note: Blessed thistle should not be mistaken for milk thistle (Silybum marianus) or other members of the thistle family.
These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.
Laboratory studies report that blessed thistle (and chemicals in blessed thistle such as cnicin and polyacetylene) has activity against several types of bacteria and no effects on some types. Reliable human study is lacking. Further evidence is necessary in this area before a firm conclusion can be drawn.
Blessed thistle is traditionally believed to stimulate stomach acid secretion and has been used as a treatment for indigestion or gas. However, there is limited scientific study in these areas. Additional research is needed before a firm conclusion can be reached.
Laboratory studies report no activity of blessed thistle against herpes viruses, influenza, or poliovirus. Effects of blessed thistle (or chemicals in blessed thistle called lignans) against HIV are not clear. Human research of blessed thistle as a treatment for viral infections is lacking.
*Key to grades:
The below uses are based on tradition, scientific theories, or limited research. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. There may be other proposed uses that are not listed below.
Adults (over 18 years old)
- Tea, tinctures, and liquid extracts are available. Traditional doses include 1.5 to 3 grams of dried blessed thistle flowering tops steeped in 150 milliliters of boiling water taken three times daily or 1 to 3 teaspoons of dried blessed thistle herb in one cup of boiling water for 5 to 15 minutes taken three times daily (sometimes recommended to be used 30 minutes before meals). 1.5 to 10 milliliters of other preparations have been taken by mouth up to three times daily. May be bitter in taste.
Children (under 18 years old)
- Not recommended due to lack of lack of reliable safety data.
The below doses are based on scientific research, publications, traditional use, or expert opinion. Many herbs and supplements have not been thoroughly tested, and safety and effectiveness may not be proven. Brands may be made differently, with variable ingredients, even within the same brand. The below doses may not apply to all products. You should read product labels, and discuss doses with a qualified healthcare provider before starting therapy.
- Allergic reactions to blessed thistle including rash may occur, as well as cross-sensitivity to mugwort and echinacea. Cross-reactivity may also occur with bitter weed, blanket flower, chrysanthemum, coltsfoot, daisy, dandelion, dwarf sunflower, goldenrod, marigold, prairie sage, ragweed, and other plants in the Asteraceae/Compositae family.
Side Effects and Warnings
- Blessed thistle is generally considered to be safe when used by mouth in recommended doses for short periods of time, with few reported side effects. Direct contact with blessed thistle can cause skin and eye irritation.
- Blessed thistle taken in high doses may cause stomach irritation and vomiting. Blessed thistle is traditionally believed to increase stomach acid secretion and may be inadvisable in patients with stomach ulcers, reflux disease (heartburn), hiatal hernia, or Barrett’s esophagus.
- Blessed thistle contains tannins. Long-term ingestion of plants containing tannins may cause gastrointestinal upset, liver disease, kidney toxicity, or increased risk of developing esophageal or nasal cancer. The effects in humans of blessed thistle tannins are not known.
- Laboratory studies suggest that blessed thistle may increase the risk of bleeding, although effects in humans are not known. Caution is advised in patients with bleeding disorders or taking agents that may increase the risk of bleeding. Dosing adjustments may be necessary.
- Many tinctures contain high levels of alcohol and should be avoided when driving or operating heavy machinery.
Pregnancy and Breastfeeding
- Blessed thistle has been used traditionally to stimulate menstruation and abortion, and therefore should be avoided during pregnancy. Although blessed thistle has been used historically to stimulate breast milk flow, it is not recommended during breastfeeding due to limited safety information. Reliable research is lacking in these areas.
- Many tinctures contain high levels of alcohol and should be avoided during pregnancy.
The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.
Interactions with Drugs
- Traditionally, blessed thistle is believed to stimulate stomach acid secretion and it may reduce the effectiveness of drugs such as cimetidine (Tagamet®), famotidine (Pepcid®), nizatidine (Axid®), or ranitidine (Zantac®).
- Based on laboratory studies, blessed thistle may increase the risk of bleeding when taken with drugs that also increase the risk of bleeding (although effects in humans are not known). Some examples include aspirin, anticoagulants (“blood thinners”) such as warfarin (Coumadin®) or heparin, anti-platelet drugs such as clopidogrel (Plavix®), and non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen (Motrin®, Advil®) or naproxen (Naprosyn®, Aleve®).
- Many tinctures contain high levels of alcohol and may cause nausea or vomiting when taken with metronidazole (Flagyl®) or disulfiram (Antabuse®).
Interactions with Herbs and Dietary Supplements
- Based on laboratory studies, blessed thistle may increase the risk of bleeding when taken with herbs or supplements that are believed to increase the risk of bleeding (although effects in humans are not known). Multiple cases of bleeding have been reported with the use of Ginkgo biloba, and fewer cases with garlic and saw palmetto. Numerous other agents may theoretically increase the risk of bleeding, although this may not be proven in most cases.
Most herbs and supplements have not been thoroughly tested for interactions with other herbs, supplements, drugs, or foods. The interactions listed below are based on reports in scientific publications, laboratory experiments, or traditional use. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy.
- This information is based on a systematic review of scientific literature edited and peer-reviewed by contributors to the Natural Standard Research Collaboration ().
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- Yang L, Lin S, Yang T, et al. Synthesis of anti-HIV activity of dibenzylbutyrolactone lignans. Bioorg Med Chem Lett 1996;6(8):941-944.
Natural Standard developed the above evidence-based information based on a thorough systematic review of the available scientific articles. For comprehensive information about alternative and complementary therapies on the professional level, go to . Selected references are listed below.